When any video is expanded into full screen mode, a very thin white frame about one pixel wide is always seen on the sides and bottom of the screen (tested on two very different systems). This can be overcome by entering full screen mode through the floating picture-in-a-picture window as described here (which is generally more correct), but I think it would be nice to be able to use full screen mode in the usual way at least if your monitor has a common resolution to diagonal ratio.
Thanks for reporting the issue @COB! I’ve opened a new ticket for this bug here: Bug #40767. Since it’s a minor issue, it likely won’t be addressed any time soon unless there are additional issues at play – however I do appreciate it’s irritating once you’ve spotted it.
Please also be aware that watching videos fullscreen will override Tor Browser’s letterboxing feature, and will contribute to your browser’s fingerprint.
Thank you for that! It’s even more than I could have expected.